I have a bad habit of closing Opera when it has opened more than 50 tabs. Needless to say, Opera could take a while to open the next time, even if I just wanted to see a single page very quickly.
So I created a batch file to make a backup of autosave.win.
Create a "session backup.bat" file and put the following code in it:
for /f "tokens=1-5 delims=:" %%d in ("%time%") do copy "autosave.win" "autosaved %date% %%d-%%e-%%f.win"
Place the batch file in the sessions folder (Open the menu item Help->About Opera and open the path that says "Saved sessions") and create a shortcut to the start menu or your desktop. Whenever you run the batch file, "autosave.win" will be copied and have added a timestamp to it.
Now you can start opera with a blank session